minor symfony#2804 Add myself to Toolkit code-owners (Kocal)

This PR was merged into the 2.x branch.

Discussion
----------

Add myself to Toolkit code-owners

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->
| Docs?         | no <!-- required for new features -->
| Issues        | Fix #... <!-- prefix each issue number with "Fix #", no need to create an issue if none exist, explain below instead -->
| License       | MIT

<!--
Replace this notice by a description of your feature/bugfix.
This will help reviewers and should be a good start for the documentation.

Additionally (see https://symfony.com/releases):
 - Always add tests and ensure they pass.
 - For new features, provide some code snippets to help understand usage.
 - Features and deprecations must be submitted against branch main.
 - Update/add documentation as required (we can help!)
 - Changelog entry should follow https://symfony.com/doc/current/contributing/code/conventions.html#writing-a-changelog-entry
 - Never break backward compatibility (see https://symfony.com/bc).
-->

For the same reasons explained in symfony#2308

Commits
-------

39c550d Add myself to Toolkit code-owners

Author: Kocal

.github/CODEOWNERS

@@ -1,3 +1,4 @@
 src/LazyImage @Kocal
 src/Map @Kocal
+src/Toolkit @Kocal
 src/Translator @Kocal